| Objective: To investigate stress distribution of normal motion postures such as forward-bending, afterward-stretching, one side bending and rotating etc. , the three-dimension analytical method of finite element was used to set up a 3-D finite element model of whole cervical spine with main muscles and ligaments, then analyzed the cause of cervical common diseases by biomechanics and movement anatomy.Methods: To build 3-D coordinate system of cervical spine model by SUPER-SAP, we measured the surface nodes of 3-D cervical spine of corpse and divided the cervical spine into 276 units (including 676 nodes) according to the finite division regulation. To observe and measure the distance and section of some muscles such as long muscle of neck, long muscle of head, sternocleidomastoid, trapezius,longissimus,inultifidus,splenius,semispinal muscle of head, semispinal muscle of neck, anterior scalene, middle scalene , posterior scalene etc., then achieved the moment of force and loaded the force in themodel . Gravity of head was added also.The condition of stress on cervical spine was changed by the force of different muscles. We calculated the changing stress and locomotion under different postures by imitated various motion such as forward-bending , afterward- stretching,one side bending and rotating by using computer.Results:1 The stress of luschka joints was mainly focused on the lower-mid under different postures. The stress increased from C2-3 to C6-7 when forward-bending. The stress was mainly focused on C4-5 , C5-6 luschka joints when afterward- stretching.2 The stress of zygapophysial joints under different postures: Strain existed in the zygapophysial joints when forward-bending, and pressure existed in the zygapophysial joints when afterward-stretching. The stress of afterward-stretching was more than double that of forward-bending.3 The stress of vertebral bodies and intervertebral discs gradually increased from C1 to C7 under different postures. The stress was the least when the muscles were relaxed. The most relative movement of intervertebral discs and biggest tensor stress of intervertebral discs existed in C4-6. Strain existed in the rear edges of vertebra bodies when forward- bending; and pressure existed in the rear edges of cervical body when afterwad-streching. Tensor stress main focused on the rear edges of vertebrabodies of C4-6.Conclusion: Under different motion postures, the main stress existed in Luschka joints, facet joints, rear edges of cervical vertebra bodies and intervertebral discs of lower-mid cervical spine. With a long -term high stress existed in these parts, the bone and tissue would be destructed and degenerated. It is significant to prevent and cure common diseases of cervical spine with this results. The 3-D finite element model of whole cervical spine with muscles and ligaments was precise imitation of normal human's anatomy. It is important to investigate, prevent and cure common diseases of cervical spine . |
